The present invention relates to a new and improved construction of high current-rectifier arrangement which is of the type comprising at least one semiconductor-rectifier element possessing contact surfaces, wherein the contact surfaces are fixedly clamped between contact bodies equipped with cooling agent-channel means, one of the contact bodies being movable and prebiased by means of spring force against the other contact body and electrically coupled by a deformable connection line or conductor with an associated connection element.
Preferred fields of application of such high current-rectifier arrangements employing the nowadays commercially available, semiconductor-rectifier elements with their very high, permissible rated currents, but comparitively low operating voltages, are, by way of example, electrolysis or heating owing to electrical power dissipation.
It is of course true that the high rated currents and their side effects demand the fulfillment of certain constructional requirements which cannot be easily satisfied. The semiconductor-rectifier element should be clamped or fixedly held between the contact bodies and these contact bodies are assigned different functions. For one thing, they must be capable of ensuring for a faultless electrical contact with low transfer or transition resistance to the rectifier element, such transition resistance must be capable of handling current intensities in the order of magnitude of many kA. Secondly, the contact bodies -- in order to ensure for the requisite contact -- must be capable of taking-up clamping forces and transmitting the same, such clamping forces should experience as small as possible change due to the unavoidable thermal expansions and the manufacturing tolerances of the different components as well as the magnetic forces prevailing therebetween. Thirdly, the contact bodies must be able to remove the unavoidable heat losses which are present under load. Furthermore, the entire construction of the rectifier must be as compact as possible, in order to provide small current paths and thus to maintain the impedance as small as possible. That the optimum fulfillment of all of these requirements is associated with great difficulties, is already manifested by the fact that due to the very high current intensities all of the conductive connections must possess quite considerable cross-sectional areas, and furthermore, as a general rule must be of massive construction.
With a heretofore know prior art rectifier arrangement of the previously mentioned type the deformable connection line or conductor consists of a connection bracket formed of copper sheet of several millimeters thickness. This connection bracket is fixedly screwed flat at one end upon the end face of the associated contact body, laterally protrudes therefrom and at the other end is flatly screwed directly with the end of the secondary winding of a transformer constructed as a connection element. The spring pressure acting upon the contact body is accomplished by a package of plate springs which act directly upon the contact body approximately at the center thereof. At the end of the connection bracket associated with the contact body there is thus machined-out an eyelet for the throughpassage of the plate springs. The free path of the connection bracket between its fixedly threaded or screwed ends can bend-through in order to compensate for the unavoidable manufacturing tolerances, but also to take-up movements which are brought about by the thermal expansion during operation. In the case of the appreciable cross-sectional area of the connection bracket, which is dictated by the rated current, there is required a force which cannot be considered to be negligible in order to bend-through such connection bracket. This force produces an undesired non-symmetry in the pre-bias emanating from the plate springs and acting upon the contact body, with the result that the contact pressure thereof acting upon the rectifier element and along therewith the transfer or transition resistance are irregularly divided over the contact surface. While it would be technically possible to provide a great bendability of the connection bracket, such only could be achieved at the expense of the compact construction of the system and while further taking into account an extension of the current path.